Industrial robot

ABSTRACT

An industrial robot comprises a stand mounted on a foot and being rotatable about a first, vertical axis, said stand supporting a first robot arm which is rotatable in relation to the stand about a second, horizontal axis. The stand comprises an underbody with two projecting parts which support an intermediate part which is rotatable in relation to the stand. The intermediate part comprises two parallel supporting elements, at the upper ends of which the first robot arm is journalled. The lower ends of the supporting elements are rotatably attachable to the underbody. The robot may thus be tilted forwards or backwards and be fixed in these positions during the robot operation, so as to obtain different types of operating ranges.

TECHNICAL FIELD

The present invention relates to an industrial robot comprising a standarranged on a foot and being rotatable about a first axis, the standcomprising a supporting plate with at least one supporting element whichsupports a first robot arm which is rotatable about a second axis.

BACKGROUND ART

A manipulator, for example an industrial robot, has a stand which isrotatably arranged on a foot fixed to a base plate and which supports afirst robot arm which is rotatable in relation to the stand. At theouter end of this arm, a second robot arm is rotatably journalled. Thissecond arm is rotatable about its own longitudinal axis and supports, atits outer end, a robot hand which is provided with a tool attachment andwhich is rotatable in two degrees of freedom relative to the second arm.To achieve movement of the mentioned robot arms and the hand, a drivemeans is arranged at each axis. Each such drive means comprises a motorand a reduction gear with a high gear ratio.

An industrial robot of the above-mentioned kind has an operating rangewhich is limited by the physical extent of the arms of the robot as wellas the mobility around the axes. An industrial robot fixed to a baseplate therefore has a given operating range within which the workpiecesto be machined by the industrial robot must be introduced. However, anindustrial robot may be used for a wide variety of tasks, and for thisreason demands are sometimes made for a changed accessibility or achanged operating range. By moving the industrial robot to a newattachment point, the operating range may be moved, but in order tochange the operating range, it is also required that the structure ofthe industrial robot be changed. This can be achieved by replacing partsof the robot, for example the stand or some of the robot arms.

From the publication "IRB 6400 Industrial Robot", ABB 6397 032-145,March 1994, an industrial robot is known in which the operating rangecan be increased by extending the second arm. This is achieved byproviding the second arm with an extension module. The operating rangecan also be changed by so-called shelf mounting, in which case anangular module is joined to the stand. This module gives the robot achanged operating range allowing it to work in front of and underitself. One problem with the described methods of increasing theflexibility of the robot by reconstructing it is that a production lossarises during the mounting time. An additional problem is that thereconstruction entails new cabling, which results in additional costs. Arobot configuration changed in this way also entails a reprogramming ofthe control equipment of the robot.

SUMMARY OF THE INVENTION

The object of the invention is to achieve an industrial robot, theoperating range of which may be adapted to different production purposeswithout any costs for rebuilding or production loss arising. Such anindustrial robot is to be capable of being adjusted, simply and in ashort time, to different types of operating ranges and different workoperations. This is achieved according to the invention by an industrialrobot in which the stand comprises adjustable supporting elements forthe first arm, allowing the robot to tilt forwards or backwards. Thesupporting elements are rotatable around a horizontal axis parallel tothe axis of the first arm and capable of being fixed to a supportingplate comprised in the stand. The supporting elements are arrangedmutually parallel and are fixed to the supporting plate with frictionjoints in fixed angular steps known to the control equipment. Thisallows the robot to be rapidly reconfigured to operating ranges of the"under body" type, in which the robot is working from below towards anobject above itself. It can also be rapidly adjusted to an operatingrange of the "shelf-mounted" type, in which the robot is working infront of and under itself as if it were placed on a shelf. The changecan be carried out without having to replace the cabling of the robot.By introducing the rotatably attachable supporting elements, the robotcan be adjusted in a very short time to a new production purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail by description of anembodiment with reference to the accompanying drawings, wherein

FIG. 1 shows a three-dimensional view of an industrial robot accordingto the invention, and

FIGS. 2a, 2b, and 2c show a side view of an industrial robot accordingto the invention with examples of a few types of working ranges whichmay be achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The industrial robot shown in FIG. 1 has a stand 2 which is rotatablyjournalled in a cylindrical robot foot 1 which is secured to a mountingbase, the stand being capable of pivoting about a vertical axis A. Thestand 2 comprises an intermediate part 5, which supports a first robotarm 8. The first robot arm 8 is pivotally journalled in the intermediatepart 5 about a horizontal axis B. At the upper end of the first robotarm 8, a second robot arm 11 is pivotally journalled about a horizontalaxis C which is parallel to axis B. The second robot arm 11 consists ofa rear part 11a, which is capable of pivoting about the axis C, and atubular front part 11b journalled in the rear part and being rotatableabout the longitudinal axis of the arm 11. The outer end portion of thefront arm part consists of a wrist 12, which comprises a wrist part 13rotatable about an axis, normally the longitudinal axis of the secondarm, and a tool attachment in the form of a turning disc 14, which isrotatable about the longitudinal axis of the wrist part 13.

The stand 2 has a U-shaped cross section, in which a first verticallyprojecting part 3a and a second vertically projecting part 3b are fixedto a lower supporting plate 4 which is rotatable around the verticalaxis A. To the vertically projecting parts 3a, 3b, the intermediate part5 is rotatably attachable around a horizontal axis B' parallel to axisB. The intermediate part 5 comprises a first supporting element 6a and asecond supporting element 6b which is parallel to the first element,between which a space 16 is created in which the first robot arm 8 canbe pivoted. The supporting elements 6a, 6b are attached to theprojecting parts 3 of the stand by means of a friction joint 17. Thesupporting elements 6a, 6b are box-shaped with an upper and a lowersemicylindrical portion. To ensure that the supporting elements 6a, 6balways move mutually parallel, they are rigidly connected to ahorizontal cross bar 7. The first robot arm 8 is pivotally journalled inthe upper ends of the supporting elements 6a, 6b.

The movement of the first robot arm around the horizontal axis B isbalanced by a first equalizer spring 9a and a second equalizer spring9b, which are articulately fixed between the upper end of the firstrobot arm 8 and the respective supporting elements 6a, 6b. The lower endof the first robot arm 8 is connected to a drive means which is fixed tothe first supporting element 6a and which comprises a motor 10a and areduction gear housed in the first supporting element 6a. The pivotingof the second robot arm 11 is performed over a parallel rod 19, thelower end of which is connected to an extended crank arm rotatable aboutthe axis B. The extended crank arm supports a counterweight 15 forbalancing the second robot arm 11, and its crankshaft is connected to adrive means which is attached to the second supporting element 6b andwhich comprises a motor 10b and a reduction gear housed in the secondsupporting element 6b.

FIGS. 2a through 2c show how an industrial robot according to theinvention may be configured to different types of operating ranges. FIG.2a shows a normal operating range 20 whereas FIG. 2b shows how the robotcan be given an operating range 21 of the "under body" type, where therobot is working from below, by providing an intermediate part 5 tiltingbackwards. FIG. 2c shows how the robot can be given an operating range22 of the "shelf-mounted" type; where the robot is able to work in frontof and under itself, by providing an intermediate part 5 tiltingforwardly.

The described industrial robot according to the invention is not limitedto comprising an industrial robot with a stand having two projectingparts 3a, 3b. The intermediate part 5, which may comprise only onesupporting element, can advantageously be fixed to a stand with only oneprojecting part. Nor is the invention limited to being applied to arobot with a counterweight 15 and a parallel rod 19, but may also beapplied to a robot without such means.

The pivoting of the intermediate part 5 is suitably carried out by adrive means connected between the supporting plate and one of thesupporting elements 6a, 6b and comprising a motor and a reduction gear.This drive means may be of a simpler kind than the drive means of therobot and may be housed in the supporting element. The operating rangeis set with the drive means whereupon the supporting element is fixed tothe supporting plate by means of the friction joint.

During the working cycle of the robot, the intermediate part 5 is fixedto the supporting plate 4 so as to form a stand 2 with a stable shape.During work, therefore, the robot functions as an ordinary industrialrobot with six degrees of freedom. This facilitates the programming ofthe control equipment. On occasions where a different operating range isdesired, the friction joint 17 is detached, allowing the intermediatepart to be rotated and adjusted into the desired position, whereupon theintermediate part 5 is again locked with the friction joint 17. The newfixed position may be known to the control equipment in advance or besensed by means of a calibration process. Such a calibration process maybe performed such that the robot in its new position is brought to sensea number of known positions, the coordinates of which are fed into thecontrol system. The locking member for fixing the intermediate part isnot limited to being a friction joint but may arbitrarily consist of amember which fixes the intermediate part to the supporting plate so thatthe loading torque of the robot can be transferred to the supportingplate.

I claim:
 1. An industrial robot comprising a foot, a stand rotatablyarranged in relation to the foot about a first axis and a first robotarm rotatably arranged in relation to the stand about a second axis,said stand comprising an underbody and at least one supporting elementwhich supports the first robot arm, characterized in that the supportingelement is rotatably arranged at the underbody and is capable of beinglocked for fixing the supporting element to the underbody during theoperating cycle of the robot.
 2. An industrial robot according to claim1, characterized in that the first axis is substantially vertical.
 3. Anindustrial robot according to claim 1, characterized in that thesupporting element is rotatable about an axis parallel to the secondaxis.
 4. An industrial robot according to claim 1, characterized in thesecond axis (B) is substantially horizontal.
 5. An industrial robotaccording to claim 1, characterized in that the drive means for themovement of the first arm (8) is arranged in the supporting element (6).6. An industrial robot according to claim 1, characterized in that thestand comprises a first supporting element and a second supportingelement, parallel to said first element, in which the first arm isjournalled and between which a space is formed, in which the first armis capable of pivoting.
 7. An industrial robot according to claim 6,characterized in that the first arm supports a second arm which isrotatable in relation to the first arm and which is connected, by aparallel rod, to a crank pivotable about the axis of the first robotarm, and that a drive means for the movement of the second arm isarranged in the second supporting element.
 8. An industrial robotaccording to claim 1, characterized in that between the underbody andthe supporting element a drive means is connected for rotating thesupporting element between the fixed positions.